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A new study suggests carbon stored in soil is entering Earth’s atmosphere faster.

When microbes feed on shriveled leaves, the carbon in those leaves enters the atmosphere as carbon dioxide.

Blame microbes and how they react to warmer temperatures. Their food of choice—nature’s detritus like dead leaves and fallen trees—contains carbon. When bacteria chew on decaying leaves and fungi chow down on dead plants, they convert that storehouse of carbon into carbon dioxide that enters the atmosphere.

In a study published August 2 in Nature, led by Pacific Northwest National Laboratory terrestrial ecology scientist Dr. Ben Bond-Lamberty, researchers show that this process is speeding up as Earth warms and is happening faster than plants are taking in carbon through photosynthesis. The team found that the rate at which microbes are transferring carbon from soil to the atmosphere has increased 1.2 percent over a 25-year time period, from 1990 through 2014.

“It’s important to note that this is a finding based on observations in the real world. This is not a tightly controlled lab experiment,” said Bond-Lamberty, who works in College Park, Maryland, at the Joint Global Change Research Institute (JGCRI), a collaboration between PNNL and the University of Maryland.

“Soils around the globe are responding to a warming climate, which in turn can convert more carbon into carbon dioxide which enters the atmosphere,” he added. “Depending on how other components of the carbon cycle might respond due to climate warming, these soil changes can potentially contribute to even higher temperatures due to a feedback loop.”

The research team also included Bond-Lamberty’s JGCRI colleague Dr. Min Chen, whose work focuses on land surface modeling and the global carbon cycle; PNNL soil scientist Dr. Vanessa Bailey; and scientists from Virginia Commonwealth University and the University of Delaware.